The present invention relates to a photoresist processing solution. More particularly, the invention relates to a photoresist processing solution useful in the development of photoresist compositions that have different solubilities in aqueous alkaline solutions upon exposure to light, and/or in the removal of selected areas of such alkali-soluble photoresist compositions.
Resin films that are decomposed or hardened by the action of external energy such as light are used as photoresists. Conventional etchants or removing agents for use in photo-decomposed or hardened areas of a photoresist are organic, strongly alkaline compounds such as tetramethyl ammonium hydroxide and trimethyl-hydroxyethyl ammonium hydroxide (also known as "choline") (in this connection, see, for example, Japanese Patent Application No. 35424/81).
In forming micropatterns on LSI (Large Scale Integration) devices, photoresist layers that have different solubilities in alkali solutions upon exposure to light are exclusively used. The principal resin component of such photoresist compositions is a novolak resin and/or a hydroxystyrene polymer, which is mixed with a quinonediazide or bisazide compound. Conventional metal-containing inorganic alkali solutions used as photoresist etchants or removers have the disadvantage of contaminating the wafers by migration of metal ions into LSI devices, and in order to avoid this problem, the use of highly concentrated aqueous solutions of tetramethyl ammonium hydroxide or choline is recommended.
However, solutions containing tetramethyl ammonium hydroxide or choline are usually so violent in action (the extent of action of course depending on the concentrations of such compounds) that they have a tendency to dissolve not only the intended areas of a resin film but also other areas which should not be attacked. On the other hand, if such solutions are diluted to an extent that no phenomenon other than the removal of a photoresist will take place in the removal step, the time necessary for photoresist removal is so prolonged that the process efficiency is reduced.